The invention relates to inductors. More specifically, the invention relates to an apparatus for winding wire around an inductor core.
High power inductors require large diameter wire that is difficult to bend. In addition, many inductors, such as a common mode inductor, have multiple phases that must be electrically insulated from one another and from the magnetic core of the inductor. Typically, the phases of the inductor are isolated by using wire that is insulated with some type of rubber material. However, this insulating material adds to the stiffness of the wire and, as a result, the wire is more difficult to bend when wrapping the wire around the inductor core.
In addition, the insulation material around a wire adds to the total diameter of the wire, making the wound inductor larger than it would be if bare, uninsulated wire were used. When winding insulated wire around the magnetic core of the inductor, the wire bulges out away from the core, making the outer diameter of the inductor much larger than it should be. Also, use of rubber insulation reduces the ability of the wire to dissipate heat that is generated when the inductor is in use.
Toroids are often the geometry of choice in designing inductor cores. Toroids offer the smallest size (by volume and weight) and lower electromagnetic interference (EMI) than other shapes used for inductor cores. Toroidal geometry leads to near complete magnetic field cancellation outside of its coil, so the toroidal inductor has less EMI when compared against other inductors of equal power rating. Toroids also have the highest effective permeability of any core shape because they can be made from one piece of material. However, toroidal inductor cores have the particular disadvantage of being difficult to wind. Also, using insulated wire can create difficulty inserting wire into the inner diameter of a toroidal inductor core, and it increases friction between the various turns of the wire.
Therefore, there is a need in the art for a high power inductor that avoids the need for using insulated wire, thereby avoiding the problems resulting from the use of insulated wire. However, the different phases of the wire must still be electrically insulated from each other and from the magnetic core.